Aircraft ski and actuating mechanism therefor



March 28, 1961 F. J. DITTER ETAL 2,977,073

AIRCRAFT SKI AND ACTUATING MECHANISM THEREFOR Filed June 21, 1956 3 Sheets-Sheet 1 I INVENTOR.

H FP/M/C/S 1 0/775? P-a [MME/f 50UCf/EA ym/emu March 28, 1961 F. J. DITTER ETAL 2,977,073

AIRCRAFT SKI AND ACTUATING MECHANISM THEREFOR 3 Sheets-Sheet 2 Filed June 21, 1956 INVENTOR. Fame/5 J 0/775? f/w/wzrr 6000/5? ATTOF/VE Y March 28, 1961 F. J. DITTER ETAL 2,977,073 1 AIRCRAFT SKI AND ACTUATING MECHANISM THEREFOR 3 Sheets-Sheet 3 Filed June 21. 1956 INVEI-VTOR. FAfl/YC/S J 0/7275? 5 fM/HETT J 601/096 JM/E. m

ATTORNEY general type, thereby 377,075 AND ACTUATING MECHANISM THEREFOR Francis 3. peter and Emmett J.- Boucher, Minneapolis, Minn., assignors to Federal Industries, Inc, a ccrpora SKI tion of Minnesota V F s V Filed June 21', 1956; SeriNot 592,943 1 can. (CL 2 62;

This invention relates to skis designed for mounting.

on an airplane landing gear, and pertains more particularly to the actuating mechanism by which each ski can be moved relative to the landing wheel with which it is associated. l I

In equipping aircraft for all-weather flights it has become customary to mount a ski adjacent to each of the two forward landing wheels, the skis being rendered retractable to permit use. of thethen lowermost wheels for landing directly" on bare ground. preciated that the compressed air contained within the tires mounted on these wheels is available for shock absorption during such alanding operation. Unfortunate- It will be ap-.

- ing in dotted outline within one ski;

ly, this pneumatic cushioning is not availablewhen a landing is efiectedon the skis themselves, and theplane experiences a correspondingly greater amount of jarring and shock on terrain of equivalent roughness or uneveness.

Accordingly,one object of the invention is to providea pneumatic shock absorbing action that is effective when theaircraft is landing on its skis, thereby permittinga landing commensurate in smoothness with that experienced during a wheel landing. Y

. Another object of the invention is to'incorporate the .A further object of the invention is to provide a,

pneumatic cushioning effect that results front-the use of moved; A

Figure 4 is a sectional view of the operating cylinder and. its piston taken in the direction of. line 44 of FigureZ;

ure 2, I w .h s Figure 6 is a sectional view whose position is inter-' compressed air, provision being'macle so that the air will have to be replenished, if at-all, only at infrequent interbe exceedingly lightweight, yet completely reliable in its The invention accordingly consists in the features of construction, combination of elements and'arrangement of parts which will be exemplified in the construction hereafterset forth and the scope of the application which will be indicated in the appended claims. In the drawings:

- Figure l is a perspective view of an airplane equipped with skis actuatable in accordance with the teachings of the present invention, the actuating mechanism appear Figure 2 is a side; elevational view of one of the skis of Figure 1, the solid line position depicting the ski in a lowercd'position for landing and the dotted line position illustrating its raised or retracted position relative to its associated wheel; t v

,Figure 3 is a fragmentary elevational view, the solid line position of which corresponds to the solid line position of Figure 2 and the two dotted line positions of the ski arm representing relative angularities that the arm would assume were the ski to beheld stationary during ancperational sequence and the wheel axle Figure 5 is a sectional view corresponding to Figure 4, but being taken in the direction of line 55 of Figmediate Figures 4 and 5 s s Figure 7 is a longitudinal sectional view taken substa'natially through the center of Figure 2, and

.Figure- 8 is. a transverse sectional view taken direction of lined-8 in Figure 7.

Referring now; in detail to the drawings, a'forw'ard in the portion of an airplane 10 is presented having typical lands ing gear 12. While the landing gear 12 may assume a variety of configurations, for the sake of drawing sim-" pli ci'ty, the gear here has been pictured as including a pair of'properly reinforced struts, one of which is completely visible in Figure 1 and the other of which has only its lower end showing. Each strut carries an axle 14 at its lower extremity, the outboard portion of whichjo'urnals a wheel 16 having mounted thereon a pneumatic tire 18 in conventional fashion.

The inboard portion of each axle 14, inythe exernplk H fied instance, supports a ski designated in its entirety a simplified actuating mechanism for .each ski that will not require elaborate. control tubing leading'nfrom the crafts cabin to the operating mechanism associated with each ski. Regarding this advantage, it'isplanncd that only onetuhe be ernployed for each ski, thereby avoiding the use of plural tubing that might otherwise increase the hazards of faulty operation throughtube damage. Stated somewhat diiferently, it is intended that-the overall length-of hydraulic tubing utilized when practicing the teachings of the instant invention be reduced appreciably over that currentlyfound in many ski installations of this invention'is to minimize wind resistance produced by the actuating mechanism itself,1it

being envisaged that'j'the operating-cylinder, together mounted within the confinesmf the ski; structure. W

'A- furth'er object 'of the invention "is tepmym an actuating mechanism of the foregoi n'g'character that' will minimizing the likelihood of tube ing; space for the wheel '16 in each instance. Superimfi;

by the reference numeral 20. Each ski is a correlation of the other, including in the illustrative situation a base shoe or runner portion 22 curving upwardly at both its, toe' 24 and heel 26. The forward half of the shoe 22 is of wider construction than the'rear half, therebyleavposed on the base shoe 2 2 and forming part of; the ski structure is an inverted channel member -28 suitably"' flanged so as to pennitattachment to its. base shoe -by I riveting, spot-welding, bolting or the like. i i i Continuing with the description of the exemplified ski construction, it will now be explained that a portion of .each channel member 28 is1cut out or removed so that a saddle 30 may be fixedly secured initsstead. These" saddles 30, one on each ski,are'each equiped with up:

standing pedestal elements 32spaced apart stiflieiently,

so as to provide an intervening space; or opening -3 4..

The opening between the. pedestals 32 of each skipro v vides accommodation'fora bell "crank arm 36 which is a 3 part of the actuating mechanismffor each of the skis.v 1'

The mid-portion of each belljcr' ank"36 is pivotally sa Patented Mar. as, 1961' ported between pedestals 32 by a transverse pin 38, whereas one end of the crank is journaled for rotation about the inboard portion of the axle 14 (or its equivalent when the axle is not used) andits other end extends downwardly through the opening 34 into the chamber formed within the interior of the ski.

The heart of the actuating mechanism for each ski is an operating cylinder 40, seen to better advantage in the sectional views presented in Figures 4-6. One end of the cylinder 40 is equipped with a head 42 apertured and provided with a suitable packing gland 44 (only generally set forth) through which a piston rod 46 projects. The rod 46 is fixedly attached at its inner endto a reciprocal piston 48 equipped with O-rings 50.

Through the agency of a nipple 2 and a tube 54 hydraulic fluid in the form of a liquid 56 may be introduced under pressure into the end of the cylinder having the head 42. Quite obviously, in actual practice a high pressure type of hydraulic coupling would serve to connect the tube 54 to the cylinder 40, there being a number of such couplings currently available. From Figure 1 it can be seen that the tube 54 leads upwardly to the cabin of the aircraft where it connects to a suitable pumping system by way of appropriate control valves so that the liquid may be forced into the cylinder 40 of each ski when it is desired to retract the skis relative to their respective wheels 16.

At the opposite or closed end of the cylinder 40 is another nipple 58 to which is attached a relatively short, length of tubing 60, being of suflicient length to lead to one side of the inverted channel member 28. Here again it might be explained that the nipple connection is only schematically depicted and that suitable high pressure coupling means would normally be employed, simplification of the drawings being achieved by not detailing a The end of the tube 60 lying remote specific coupling. from the cylinder, that is the end located adjacent the channel member 28, is provided with normally closed valve 62 of conventional construction but of course adequate to withstand the relatively high pressures to which it is at times subjected, for instance the 1100 p.s.i. hereinafter mentioned. A valve cap 64 is applied to the end of the valve 62. From Figure 1 it will be discerned that the valve 62 is'fixedly secured to the material constituting the channel member 28 and thereby is readily accessible for filling purposes. However, it is to be noted that the tube 60 terminates at the side of the ski 20 and therefore there is no external tubing associated with this feature of the invention, there being only the single tube 54 for each.

ski.

Pivotal connection is established between the closed end of the cylinder 40 and a fixed portion of the ski structure 20 by means of an integral ear 66 formed on the cylinder having a transverse aperture 68 through which extends a pin 70, the pin engaging a clevis and bracket 72 which may be riveted, welded or otherwise affixed to the ski. The piston rod 46, on the other hand, is pivotally attached to the lower end of the bell crank arm 36 by reason of a pin 74.

As a practical matter it may be pointedout that each ski 20 is equipped with forward and aft shock cord rigging 76 and 78, respectively. Since the rigging 76 and 78 may be of conventional construction, the stabilizing purpose of which is well known, the various parts thereof need not be described with any degree of particularity, it is believed.

From the foregoing description it is thought that the mode of operation will be readily apparent.

which the actuating mechanism functions may well prove tribe of benefit.

However, further comment directed specifically to the manner in square inch, via the valve unit 62. Without hydraulic pressure suflicient to overcome this air pressure, the piston 48 will be urged to the right as viewed in Figure 4. This is the extended position of the ski relative to its associated wheel 16 (see Figure 2). It will be recognized that the piston rod 46 causes a counter-clockwise rotation of the bell crank arm 36 (Figure 2), for the closed end of the cylinder 40 is fixed except for its ability to pivot about the pin 70, and that this rotational movement lowers the ski.

Assuming now that the piston 48 has been permited to move into the position depicted in Figure 4 by virtue of the compressed air, the skis 20 are then extended Accordingly, at this time reference should be had to is charged with compressed air, say 220 pounds per.

below the tires'18 preparatory to effecting 'a 'ski landing. When the skis 20 engage the ice or snow covered ground during the landing operation, the force is such that the bell crank 36 of each ski will be urged in a clockwise direction (Figure 2) wi th the consequence that the piston 48 will be moved to the left'(Figure 6), thereby compressing the air contained within the cylinder 40 that we have assumed above to have an original or initial pressure of 220 p.s.i. The amount of-additional compression will of course vary depending upon the pilots ability to land smoothly and other factors. Therefore, we will presume that the Figure 6 position represents, say, only a static loading, i.e., represents just the weight of the plane itself. Typically, this may cause an air compression to a value of say, 265 p.s.i. any shock resulting from the landing operation producing a compression of greater magnitude.

To give a general idea as to the relative angular positions that the bell crank 36 will assume in shouldering the above-mentioned static load, attention is to be directed to Figure 3. For simplicity of illustrationFigure 3 is presented with the ski 20 remaining stationary and with the axle 14 moving instead. Hence, the top dotted line position of the bell crank arm is indicative of the relative position pictured in Figure 6.

Proceeding now to what is done to effect a retraction of the skis 20 for a wheel-type landing, attention should be shifted to Figure 5. Here liquid has been introduced into the cylinder-40 under suflicient pressure from the cabins pumping system via the tube 54 to cause travel of the piston 48 to the left. This, for example, may cause compression of the air to, say 1100 p.s.i. At any rate piston rod 46 exerts a pull on the bell crank 36 so as to cause a clockwise rotation thereof about the axle 14 (Figure 2), thereby lifting or retracting the ski 20 relative to its associated wheel 16 and tire 18. Reference should at this time be had to the lower dotted line position of the arm 36, as seen in Figure 3, this view presenting the greatest relative angular movement between said bell crank arm and the ski.

When the pressure applied to the piston 48 by the liquid 56 is reduced, say, back to a value less than our first-mentioned 220 pLs.i. the piston 48 will return to its Figure 4 position to extend or lower once again the ski. Especial note should be'taken that escape of air past the piston 48 is virtually impossible owing chiefly to the liquid 56 and the'pressure to which it is subjected. However, should the air need replenishing as a result of aprolo'nged shut down or inspection, this can readily be effected by way of the valve unit 62, suitable access I being had thereto at the-side of each ski. It should also I be borne in mind that only a single exterior tube 54 is necessary for. each actuating mechanism, thus reducing the chances of tube failure during flight or while landing.

Further, the actuating mechanism is so designed that it.

can be mounted almost entirelywithin the confines of the ski it is to move. e

As many,changescould be made in the above construction and many apparently widely different embodiments ofthe invention could be made without departing from the scope thereof, it is intended that all matter contained in, the above description or shownin theuac companying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the following claim is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of'language, might be said to fall therebetween.

What is claimed: 1 i

In combination with an aircraft provided with a landing gear having a wheel rotatably carried thereon, an aircraft ski associated with said wheel provided with a bottom runner portion, a bell crank having an upper end pivotally connected to said landing gear, an intermediate portion pivotally connected to a portion of said ski above said runner portion and having its lower end directed toward said runner portion, a cylinder extending generally longitudinally of the ski having a normally closed end pivotally anchored to a portion of the ski nearer the forward end of said ski, a reciprocable piston within the cylinder having a piston rod projecting from the other end of said cylinder, the projecting end of said piston rigging connected at one end to the forward end of the ski and at its other end to the aircraft, and means for introducing liquid under pressure into, said other end of the cylinder to cause said lower end of the bell crank to traverse'an are so as to raise said ski relative to said wheel, whereby release of liquid pressure will permit return of said ski to its lowered position relative the wheel when sufiicient air is confined between said piston.

and the closed end of said cylinder, said air being compressed when said piston moves toward said closed end.

References Cited in the file of this patent UNITED STATES PATENTS 20' 2,193,736 Onions 'Mar. 12, 1940 2,294,918 Levy Sept. 8, 1942 2,532,611 Ditter Dec. 5, 19-50 

